FFI: Eliminate string fallbacks in error wrappers (payjoin#1127)

Author: spacebear21

payjoin-ffi/src/ohttp.rs

@@ -1,17 +1,9 @@
 pub use error::OhttpError;
 
 pub mod error {
-    #[derive(Debug, PartialEq, Eq, thiserror::Error, uniffi::Object)]
-    #[error("OHTTP error: {message}")]
-    pub struct OhttpError {
-        message: String,
-    }
-    impl From<ohttp::Error> for OhttpError {
-        fn from(value: ohttp::Error) -> Self { OhttpError { message: format!("{value:?}") } }
-    }
-    impl From<String> for OhttpError {
-        fn from(value: String) -> Self { OhttpError { message: value } }
-    }
+    #[derive(Debug, thiserror::Error, uniffi::Object)]
+    #[error(transparent)]
+    pub struct OhttpError(#[from] ohttp::Error);
 }
 
 impl From<payjoin::OhttpKeys> for OhttpKeys {

payjoin-ffi/src/uri/error.rs

@@ -4,8 +4,8 @@ pub struct PjParseError {
     msg: String,
 }
 
-impl From<String> for PjParseError {
-    fn from(msg: String) -> Self { PjParseError { msg } }
+impl PjParseError {
+    pub(crate) fn from_err(err: impl std::fmt::Display) -> Self { Self { msg: err.to_string() } }
 }
 
 #[derive(Debug, PartialEq, Eq, thiserror::Error, uniffi::Object)]
@@ -14,8 +14,10 @@ pub struct PjNotSupported {
     msg: String,
 }
 
-impl From<String> for PjNotSupported {
-    fn from(msg: String) -> Self { PjNotSupported { msg } }
+impl PjNotSupported {
+    pub(crate) fn from_display(uri: impl std::fmt::Display) -> Self {
+        Self { msg: uri.to_string() }
+    }
 }
 
 #[derive(Debug, thiserror::Error, uniffi::Object)]

payjoin-ffi/src/uri/mod.rs

@@ -20,10 +20,9 @@ impl From<payjoin::Uri<'static, NetworkChecked>> for Uri {
 impl Uri {
     #[uniffi::constructor]
     pub fn parse(uri: String) -> Result<Self, PjParseError> {
-        match payjoin::Uri::from_str(uri.as_str()) {
-            Ok(e) => Ok(e.assume_checked().into()),
-            Err(e) => Err(e.to_string().into()),
-        }
+        payjoin::Uri::from_str(uri.as_str())
+            .map(|e| e.assume_checked().into())
+            .map_err(PjParseError::from_err)
     }
     pub fn address(&self) -> String { self.clone().0.address.to_string() }
     /// Gets the amount in satoshis.
@@ -36,10 +35,11 @@ impl Uri {
     }
 
     pub fn check_pj_supported(&self) -> Result<Arc<PjUri>, PjNotSupported> {
-        match self.0.clone().check_pj_supported() {
-            Ok(e) => Ok(Arc::new(e.into())),
-            Err(uri) => Err(uri.to_string().into()),
-        }
+        self.0
+            .clone()
+            .check_pj_supported()
+            .map(|uri| Arc::new(uri.into()))
+            .map_err(PjNotSupported::from_display)
     }
     pub fn as_string(&self) -> String { self.0.clone().to_string() }
 }